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| United States Patent |
5,288,295
|
|
Hypes
, et al.
|
February 22, 1994
|
Cement kiln fuels containing suspended solids
Abstract
A fuel comprised of liquid and solid refinery waste streams is described.
The fuel is a blend of a heavy paraffinic oil, an emulsified waste oil,
water and solids. The fuel is blended both to achieve a viscosity which
enables the fuel to be pumped, and to obtain the required fuel value for
burning in a cement kiln while simultaneously having a high solids
content. The amount of the heavy paraffinic oil present in the final fuel
is related to the ambient temperature at which the fuel is to be pumped,
stored and consumed. Typically, the higher the ambient temperature the
more heavy paraffinic oil that can be used in the fuel blend.
| Inventors:
|
Hypes; Ron (Foster City, CA);
Morton; Peter (East Palo Alto, CA)
|
| Assignee:
|
Romic Chemical Corporation (East Palo Alto, CA)
|
| Appl. No.:
|
015261 |
| Filed:
|
February 8, 1993 |
| Current U.S. Class: |
44/301; 44/300 |
| Intern'l Class: |
C10L 001/32 |
| Field of Search: |
44/301,300
|
References Cited
U.S. Patent Documents
| 3659786 | May., 1972 | Vier | 110/346.
|
| Foreign Patent Documents |
| 56-159291 | Dec., 1981 | JP.
| |
| 57-111388 | Jul., 1982 | JP.
| |
| 59-81386 | May., 1984 | JP.
| |
| 2036072 | Nov., 1979 | GB.
| |
Other References
CRC, Handbook of Chemistry and Physics, 51st Edition, 1970-71, pp.
F-224-F-225.
|
Primary Examiner: Willis, Jr.; Prince
Assistant Examiner: Silbermann; James
Attorney, Agent or Firm: Limbach & Limbach
Parent Case Text
This is a continuation of co-pending application Ser. No. 07/738,303 filed
on Jul. 31, 1991, now abandoned.
Claims
What is claimed is:
1. A fuel for use in combustion in a cement kiln which comprises:
a) a heavy paraffinic oil having an average pour point of 80.degree. F., an
average density of 7.8 lbs./gallon, less than 0.1% Basic Sediment & Water,
less than 10% asphaltene content and an API gravity in the range of
12.degree. to 18.degree. API; and,
b) an emulsified waste oil having a pour point less than 10.degree. F., an
average density of 6.8 lbs./gal., Basic Sediment & Water concentration in
the range of 0.5 to 5.0%, and API Gravity in the range of 36.degree. to
42.degree. API:
c) solid particles constituting at least 36% of the weight of said fuel
having particles sizes in the range of 10.mu. to 5000.mu. and oil
impregnated on the surface of said particles
wherein said components are mixed together such that the suspended solids
are stably suspended in the resulting fuel, the resulting fuel has a
viscosity of 1000-4000 cps at 25.degree. C; and the resulting fuel has a
fuel value in excess of 8000 BUT/lb.
2. A fuel according to claim 1 wherein said heavy paraffinic oil is
selected from the group consisting of lube oil extract, heavy vacuum gas
oil, combined fluidized bed catalytic cracking unit feed, crude oil tank
bottoms, and mixtures thereof.
3. A fuel according to claim 1 wherein said emulsified waste oil is
selected from the group consisting of American Petroleum Institute
separator oil skimming stream, desalter oily bleed to sewer stream, and
mixtures thereof.
4. A fuel according to claim 1 wherein said solids are selected from the
group consisting of API separator belt press cake, storage tank bottoms,
oily sewer sludge, F037 and F038 classified wastes, and mixtures thereof.
5. A fuel according to claim 1 wherein said solids are selected from the
group consisting of K-waste, attapulgite filtration clays, sands, silts,
SiO.sub.2, alkali metal salts, alkaline earth metal salts, ferric sulfide,
cupric sulfide, ferrous oxide, metal carbonates, metal sulfates, metal
chlorides, and mixtures thereof.
6. A fuel according to claim 1, further comprising water.
7. A fuel according to claim 6 for use at ambient temperatures below
40.degree. F. wherein said fuel liquid phase components are present:
heavy paraffinic oil in the range of 10 to 45% by weight of the liquid
phase;
emulsified waste oil in the range of 40 to 85% by weight of the liquid
phase;
emulsified waste oil in the range of 40 to 85% by weight of the liquid
phase; and,
water in the range of 0.1 to 20% by weight of the liquid phase.
8. A fuel according to claim 6 for use at ambient temperatures above
40.degree. F. wherein said fuel liquid phase components are present:
heavy paraffinic oil in the range of 25 to 80% by weight of the liquid
phase;
emulsified waste oil in the range of 5 to 50% by weight of the liquid
phase; and,
water in the range of 0.1 to 25% by weight of the liquid phase.
9. A method of disposing of refinery wastes which comprises the steps of:
blending a cement kiln fuel having a heavy paraffinic oil component, an
emulsified waste oil component, a water component and a solids component
to obtain a fuel which can be pumped and which has a fuel value in excess
of 8000 BUT/lb.;
burning said cement kiln fuel in a cement kiln to obtain a cement product,
carbon dioxide and water emissions.
Description
TECHNICAL FIELD
This invention relates generally to fuels derived from petrochemical and
crude oil refining waste products, and more particularly, this invention
relates to the suspension of substantial amounts of solids in fuels while
maintaining viscosity and fuel value specifications.
BACKGROUND OF THE INVENTION
Hazardous waste disposal has become more difficult as stricter solid waste
disposal and air emissions standards have been implemented. In
petrochemical and crude oil refining, both liquid wastes and solid wastes
are generated which must be safely and economically treated to alleviate
the hazards associated with the waste streams. Since there is often an
inherent fuel value associated with many refinery wastes streams, disposal
procedures have been developed to burn such waste stream fuels in furnaces
and kilns in order to recover the fuel value, while reducing both the
nature and volume of the waste stream from large volumes of complex
organic molecules to simple carbon dioxide and water combustion products.
This form of waste utilization reduces the volume of the original waste
stream. It also degrades the hazardous molecules to environmentally
acceptable products.
The disposal of solid waste products generated during petroleum refining
poses an even more challenging opportunity. These solid wastes are
diverse, having been generated in filtering, reactor processing and
settling process steps. Sometimes, the solids are metal salts requiring
special disposal techniques. Often, these solid materials are coated or
infiltrated with hydrocarbon molecules, making their disposal more
complex, and their retention in hazardous waste disposal sites expensive.
The present invention provides fuel compositions and methods of making such
fuels whereby certain refinery waste streams having adequate fuel value
are advantageously combined with refinery solid wastes to obtain a fuel
for use in cement kilns. The cement kiln provides a process environment in
which high kiln temperatures insure adequate degradation of the heavy
organic molecules. Simultaneously, the cement kiln provides a matrix of
solid cement particles which are chemically compatible with the solid
particles resulting from the refinery solid wastes so as to obtain an
acceptable cement product.
Fuels made according to the present invention must meet several criteria in
order to qualify as cement kiln fuels. The two most important
specifications are that the fuel containing solids must be pumpable in
varying outdoor temperatures, and it must provide adequate fuel value so
that high temperatures can be maintained in the cement kiln. Both of these
criteria are in conflict with the refiner's objective of disposing of the
maximum mass of waste solids in the lowest fuel value stream. These
disparate factors are satisfactorily resolved in the present invention
which provides for fuels with high solids content and adequate fuel value
for cement kiln applications.
SUMMARY OF THE INVENTION
The fuels of the present invention comprise at least four components: (i) a
heavy paraffinic oil such as lube oil extract, heavy vacuum gas oil,
combined fluidized bed catalytic cracking unit ("FCCU") and crude tank
bottoms; (ii) an emulsified waste oil, e.g., American Petroleum Institute
("API") separator oil skimmings or desalter oily bleed to sewer; (iii)
water from pond, sewer, sour condensate or various brines; and, (iv)
solids from API separator belt press cake, storage tank bottoms, oily
sewer sludge, or F037 or F038 (Federal EPA waste descriptor
classifications defined in 40 C.F.R. .intg.261.13(b) (2)) in the
subsurface.
In order to meet the pumpability and fuel value criteria established for
cement kiln operation, the fuel is comprised of the above components mixed
in proportions which are related to the ambient temperature for transport,
storage and consumption of the fuel. For ambient temperatures below
40.degree. F., the fuel is mixed to obtain a heavy paraffinic oil content
in the range of 10 to 45% by weight in the liquid phase, an emulsified
waste oil content in the range of 40 to 85%, by weight, and added water
content in the range of 0.1 to 20% by weight. For ambient temperatures in
excess of 40.degree. F., the fuel may be blended in different proportions:
heavy paraffinic oil content in the liquid phase of 25 to 80% by weight,
an emulsified waste oil content in the range of 5 to 50% by weight, and
added water content in the range of 0.1to 25% by weight. In both fuels, it
is possible to add up to 70% solids by weight of the entire fuel mixture.
The solids content will be determined by reference to the minimum fuel
value and viscosity. The resulting fuels should have a viscosity of 1000
to 4000 cps at 76.degree. F., a density of 8.2 to 8.9 pounds/gallon, high
lubricity, 6 to 14% weight ash, and a fuel value in excess of 10,000
BTU/lb. The resulting fuels are characterized as thixotropic.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a plot of fuel value as a function of solids content for fuels
according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The heavy paraffinic oil component of the fuel typically has an average
pour point of 80.degree. F., an average density of 7.8 lbs./gallon, Basic
Sediment and Water ("BS & W") less than 0.1% total, an asphaltene content
below 10% and an API Gravity in the range of 12.degree. to 18.degree..
Common refinery sources of the heavy paraffinic oil component include lube
oil extract, heavy vacuum gas oil, combined FCCU feed, and crude tank
bottoms. Other sources are possible.
The emulsified waste oil component of the fuel is characterized by an
average pour point less than 10.degree. F., a density of about 6.8
lbs./gallon, BS & W in the range of 0.5 to 5.0%, and API Gravity in the
range of 36.degree. to 42.degree. API. The emulsified waste oil component
can be obtained from API separator oil skimmings and desalter oily bleed
to sewer. Other sources are possible depending upon refinery operating
conditions.
The solid component of the fuel can be obtained from diverse sources such
as API separator belt press cake, storage tank bottoms, oily sewer sludge
and F0376 and F038 in the subsurface. Additional refinery solids sources
include K-waste (a Federal EPA waste descriptor classification defined in
40 C.F.R. .sctn.261.13(b) (2)), attapulgite filtration clays for kerosine,
Jet A, JP-4, JP-5, coalescing beds, sand beds or other materials formed at
polar and non-polar boundaries typified by oil-water emulsion boundaries.
The solids are typically one or more of sands, silts, SiO.sub.2, alkali
metal salts, alkali earth metal salts, ferrous sulfide, cupric sulfide,
ferrous oxide, ferric oxide, metal carbonates, sulfates, chlorides and
other halides. Solid particle size is typically in the range of 10.mu. to
5000.mu..
It is also desirable that the solid particles are oil impregnated on their
surface prior to their addition to the fuel. We have noted that diesel and
kerosene coated solids do not suspend as well as those solids coated with
higher boiling constituents. If the solids are not already associated with
a stream containing water, it is advisable to test the solids for the
presence of hydrophilic sites which will react with the water component of
the fuel. These hydrophilic sites can be determined by thoroughly
dispersing 100 grams of the solids in 100 grams of xylene or tetradecane
through vigorous mixing. An observable increase in the viscosity of the
solution or any agglomeration of the particulates when adding successive 1
ml aliquots of water up to 200 ml is indicative of the desired hydrophilic
sites.
Before blending the components to obtain a fuel, it is first necessary to
pre-select a desired final viscosity related to the ambient environment in
which the fuel will be transported, stored and consumed. Once this
selection has been made, the heavy paraffinic oil component and the
emulsified waste oil component can be blended together in the proportions
set forth above. Generally, for fuels to be used at temperatures above
40.degree. F., the heavy paraffinic oil component is added in higher
amounts than the emulsified waste oil component. Conversely, for fuels to
be used at temperatures lower than (40.degree. F.), the heavy paraffinic
oil component is added in proportionately smaller amounts. The ideal
mixing temperature for combining the two oil components is below
45.degree. C. We have obtained satisfactory results when these two
components have been blended together at 30.degree. C. At higher
temperatures, the heavy oil coating will strip off of the solids making it
difficult to suspend them in the fuel. This high temperature separation is
apparent when the surface of the finished fuel blend appears to be sandy
or granular when agitated.
After the heavy paraffinic oil and emulsified waste oil have been blended
together, it is preferred to add the solids next. Then, the addition of
water into the fuel disperses the solids in a manner consistent with
micelle formation. Accordingly, the solids are distributed evenly in the
final fuel. If the solids contain sufficient water, it may not be
necessary to add any more to the fuel. It is preferred to wait until the
solids have been dispersed throughout the fuel and it appears homogeneous,
before determining whether to add more water.
In the proper temperature range, solids addition will quickly cause the
fuel to appear waxy or gelatinous. This effect becomes more pronounced as
the weight percent of solids exceeds 30%. The waxes coming out of solution
do not have the normal amorphous look of solid wax. Here, the appearance
is consistent with nucleation on the surface of the suspended solids
rather than the typical intermolecular Van Der Waals attractions.
If the water concentration is too low, an initial wax formation is obtained
with solids addition. Within ten to fifteen minutes after solids addition,
the solids will destabilize and settle to the bottom of the process
vessel. This solids destabilization can be reversed by increasing the
water concentration to the proper level.
Low shear mixing is preferred over high shear mixing. The waxes, once out
of solution, do not tolerate high shear.
If the mixing equipment has power sensing capabilities, or if a viscometer
is used, the thixotropic nature of the fuel may now be observed. We have
obtained superior results by progressively increasing the mixing speed
until mixer tip velocities exceed 12 miles per hour (using a Fawcett Mixed
Flow Impeller marked with U.S. Pat. No. 2,787,448.)
We have observed an interesting phenomena with respect to the relationship
between fuel viscosity and the amount of water added to the fuel. Added
water is, in this instance, distinguished from intrinsic water which is
introduced to the system through its association with the other fuel
components. Our observations indicate that following an initial viscosity
maxima just beyond the viscosity at zero water added, the viscosity
decreases to a minima below the fuel viscosity with zero water added. This
means that the addition of water to the fuel beyond the maxima will cause
a decrease in viscosity and thus makes the fuel more pumpable. At some
point beyond this minima the addition of water will cause gel formation,
and the undesirable breakdown of the fuel suspension into non-homogeneous
gel clumps. We are presently investigating this phenomena more thoroughly
to quantify this relationship between viscosity and water added.
We have also developed additives which may be added to the blended
thixotropic fuel in order to minimize oil-water phase separation during
storage and to enhance total combustion of all hydrocarbon components in
the fuel. The enhanced combustion additive may be important when this fuel
is burned as a fuel in cement kilns in order to reduce or eliminate the
total hydrocarbon content of the cement kiln stack gases. Another
component called the carbon monoxide combustion promotor may be added to
reduce or control carbon monoxide levels resulting from inefficient fuel
combustion and the naturally high alkaline (calcium carbonate) content of
the raw material feed to the cement kiln.
Alphaolefin sulfonates and other surface active dispersants can be used as
additives for minimizing oil water phase separation and for enhancing
solids dispersion and stabilization within the fuel.
Overbase magnesium oxide compounds can be added as the combustion enhancer
to insure complete combustion of the hydrocarbon fuel. This additive helps
to reduce or eliminate the hydrocarbon content of cement kiln stack gases.
A precious metal oxide is used as an additive to promote the combustion of
carbon monoxide which may result from incomplete combustion of the cement
kiln fuel. Some representative catalysts for this purpose include
PtO.sub.2 and PtO.sub.2 /ReO.sub.2.
The present invention will now be described with reference to working
examples.
EXAMPLES 1 THROUGH 10
A series of fuels were made according to the present invention using lube
oil from Sun Refining and Marketing Company, Tulsa, Oklahoma. The lube oil
was characterized by 85.degree. F. pour point, density of 0.92 g/cm.sup.3,
no BS & W concentration, and no asphaltene concentration. The fuel
included emulsified waste oil having 0.85 g/cm.sup.3 density, 0.5% BS & W,
35.3 API Gravity, and also included water and belt press cake. The cake
included particles in the 50.mu. to 5000.mu. range and were oil
impregnated. These components were blended together in a specific order.
The heavy paraffinic oil ("heavy") and emulsified allowed to cool to
82.4.degree. F. The solids were added quickly (complete in about two
minutes) and mixed at 2000 rpms using a 48 mm Fawcett Mixed Flow Impeller
for about twenty minutes or until the fuel was homogeneous. Mixing of the
sample caused an initial temperature rise to 86.degree. F. for all samples
except Experiment 4 which rose to 94.degree. F. If the sample required
water, it was added after the fuel appeared homogeneous. Total sample mass
was 500 to 700 grams. All samples were mixed for forty additional minutes
or until homogeneous whichever was longer. Temperatures were adjusted by
ice bath when necessary.
After the fuels were mixed, samples were subjected to bomb calorimetry
(ASTM Method D 240-87) and viscosity measurement using a Brookfield Model
LVF with #2 spindle at 6 rpms.
The results of these tests are shown in Tables 1 and 2.
TABLE 1
__________________________________________________________________________
EXPERIMENT 1
EXPERIMENT 2
EXPERIMENT 3
EXPERIMENT 4
EXPERIMENT 5
WT % WT % WT % WT % WT %
COMPONENTS
TOTAL
LIQ.
TOTAL
LIQ.
TOTAL
LIQ.
TOTAL
LIQ.
TOTAL
LIQ.
__________________________________________________________________________
HEAVY OIL
22.5%
41 10.2%
17.3
45.5%
77 30.7%
77 18.5%
77
LIGHT OIL
22.5%
41 40.6%
68.9
4.5% 8 3.0% 7.5 1.8% 7.5
WATER 10.0%
18 8.1% 13.8
8.0% 15 6.1% 15.5
3.7% 15.5
SOLIDS 45.0% 41.1% 41.0% 60.2% 76.0%
FUEL VALUE
11,600 12,500 12,700 11,100 9.800
BTU/LB
VISCOSITY
3,000 cps
1,050 cps
2,000 cps
3,825 cps
3,700 cps
TEMP OF 4.degree. C.
4.degree. C.
25.degree. C.
25.degree. C.
35.degree. C.
FUEL AT
VISCOSITY
__________________________________________________________________________
TABLE 2
__________________________________________________________________________
EXPERIMENT 6
EXPERIMENT 7
EXPERIMENT 8
EXPERIMENT 9
EXPERIMENT 10
WT % WT % WT % WT % WT %
COMPONENTS
TOTAL
LIQ.
TOTAL
LIQ.
TOTAL
LIQ.
TOTAL
LIQ.
TOTAL
LIQ.
__________________________________________________________________________
HEAVY OIL
39.7%
81.7
50.5%
79.2
42.5%
74.7
30.1%
50.9
25.4%
50.9
LIGHT OIL
8.9% 18.3
13.2%
20.8
11.1%
19.5
15.2%
25.5
12.9%
25.7
WATER 0 0 0.0% 0 3.3% 5.8 13.8%
23.6
11.7%
23.4
SOLIDS 51.4% 36.3% 43.1% 40.9% 50.0%
FUEL VALUE
12,100 14,900 13,500 11,900 11,200
BTU/LB
VISCOSITY
1,050 cps
2,000 cps
4,000 cps
1,000 cps
1,200 cps
TEMP OF 25.degree. C.
25.degree. C.
25.degree. C.
25.degree. C.
25.degree. C.
FUEL AT
VISCOSITY
__________________________________________________________________________
The results as shown in Tables 1 and 2 illustrate that the four components
when blended yield high-solids fuels of multiple viscosities with large
BTU/lb. values. Experiments 1 and 2 shown that a stable low temperature
fuel with variable flow characteristics may be made while solid suspension
is above 40 percent and fuel value stays above 11,500 BUT/lb. Experiments
3, 4 and 5 (shown in Table 1 and FIG. 1) depict high solids concentrations
for fuels with relatively constant liquid component ratios. Thus, higher
viscosities may yield fuels of extraordinary solids concentrations with
high BTU/lb. values. Experiments 6 and 7 demonstrate zero-water addition
fuels which have high solids content, high BTU/lb. values and low
viscosities. Experiments 8, 9 and 10 show the variety of compositions the
fuels may achieve at room temperature. Experiment 8 fuel has a low water
and high heavy oil content to yield a high viscosity, high solids, low
water fuel. Experiments 9 and 10 show that more water and light oil yields
high-solid fuels of excellent viscosity with only slight fuel value
decreases.
While the foregoing invention has been described with reference to
particularly preferred embodiments, these embodiments are not intended to
limit the scope of the present invention, but instead are intended to
illustrate the invention. Those of ordinary skill in the art will
appreciate that variations and modifications to the embodiments described
here are still within the scope of the present invention.
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